Trolleys are devices which may run along a rail installed on a ceiling while carrying an object to be transferred. Trolleys described above are generally used in places where transfer of a heavy weight is needed, such as various industrial settings, docks, and vessels.
General trolleys each include a plurality of wheels, a supporting plate unit which runs along a rail having the form of an H-beam or an I-beam, and a link unit provided in the supporting plate unit to carry an object to be transferred. The link unit may carry the object to be transferred through a winding device such as a chain block. Also, a worker may transfer a trolley on which an object hangs through pushing or pulling. As a cited reference, U.S. Pat. No. 4,343,240 (Aug. 10, 1982) and U.S. Pat. No. 4,248,157 (Feb. 3, 1981) may be referred to.